It is said that an HCFC-based refrigerant represented by R22 presently utilized in an air conditioner destroys an ozone layer due to the stability of physical properties thereof.
In recent years, an HFC-based refrigerant has been started to be utilized as a substitute for the HCFC-based refrigerant. However, the HFC-based refrigerant has a nature that it promotes the global warming phenomenon.
Therefore, recently, the employment of an HC-based refrigerant which does not cause the destruction of the ozone layer and the global warming phenomenon is being examined.
However, this HC-based refrigerant is flammable and hence, it is necessary to previously prevent the explosion and ignition of the HC-based refrigerant and to ensure the safety.
Therefore, there are proposed methods for previously preventing the explosion and ignition of the HC-based refrigerant, wherein the igniting source is eliminated or isolated, or placed remotely (for example, see Japanese Patent Application Laid-open Nos.7-55267 and 8-61702).
In the methods in which the igniting source is eliminated, it has been proposed that a non-contact relay generating no spark is used, ora contact portion is sealed. With this method, however, the part or component used is limited, but also it is difficult to completely eliminate sparks in all the parts or a control section.
In the methods in which such part or component are isolated from a place where there is a possibility that the refrigerant may be leaked. In the methods in which the igniting source is placed remotely, it has been proposed that a part accommodating box is placed in an outdoor unit of the air conditioner, or outside a housing of a refrigerator. However, such methods brings about a disadvantage in a respect of space, but also possibly causes an electric leakage or a short-circuit due to the leading-about of wires.
Accordingly, the present invention has been accomplished by paying an attention to the fact that even if a flammable gas is ignited, the flames are not propagated, if flat plates are spaced at a certain distance or less apart from each other, and it is an object of the present invention to ensure that even if the ignition occurs due to the generation of sparks or the like, the flames are prevented from being propagated, thereby preventing the occurrence of the serious explosion or fire.